The subject matter disclosed herein relates to earplugs and a method of assembling an earplug.
Hearing protection devices (HPDs) may be broadly categorized into earplugs, which are placed into or against an entrance of an ear canal of a user to form a seal and block sound (insert or semi-insert), earmuffs, which fit over and around the ear (circumaural) to provide an acoustic seal against the head, and helmets, which normally encase the entire head of the user. Earplugs are typically made from materials such as slow-recovery closed-cell foam, vinyl, silicone, elastomer formulations, spun fiberglass and cotton/wax combinations. They may be grouped into the categories of foam earplugs, pre-molded earplugs, formable earplugs, custom molded earplugs and semi-insert earplugs.
Foam earplugs are generally made from either slow-recovery PVC or polyurethane closed-cell material, both of which provide similar amounts of sound attenuation. PVC earplugs are commonly punched from sheets of foam to have simple contours with parallel sides and cylindrical or hexagonal footprints. Polyurethane earplugs are molded to have shapes like bullets or bells and may have asymmetrical features like ridges. Since their introduction, foam earplugs have become widely used because they are generally comfortable to wear and they provide a high degree of amount of sound attenuation. They can, however, be difficult for some users to insert fully and properly.
Pre-molded earplugs, on the other hand, are formed from flexible materials, including foam, into conical, bulbous or other shapes and are typically affixed to or enshroud a flexible stem for handling and insertion. Users can, therefore, grip the stem and push the earplugs into place in the ear canal whereupon an acoustic (pneumatic) seal is made against the canal walls.
Foam earplugs or pre-molded earplugs can, therefore, be used by students taking tests who want to have an amount of ambient sound attenuated or by musicians in concert, flight deck personnel or employees on the floor of a manufacturing plant who are exposed to extremely loud sounds that would otherwise impair their hearing after prolonged exposures. In each case, the effectiveness of the earplugs depends greatly on the amount and types of sounds that are attenuated, the comfort users experience when the earplugs are worn, the ability of the users to insert their earplugs safely into their ear canals and the ability of the users to remove their earplugs safely when desired.
Often, however, the factors that relate to the effectiveness of earplugs can be in conflict with one another. For example, an earplug whose tip is very dense may attenuate a large amount of sound but may also be very uncomfortable to wear. Meanwhile, an earplug that is less dense may be very forgiving but may not attenuate a sufficiently large amount of sound and could be difficult to insert properly. Similarly, an earplug that comes equipped with a relatively stiff stem may be easy to insert into an ear canal, but the same earplug may be dangerous if the stem were subject to an impact that forced the earplug deep into the ear canal.